The present invention relates to a sequential radial mirror analyser, particularly but, not exclusively for electron/ion microscopes.
Energy spectrometers for electron/ion microscopes are often used for analytical techniques such as Auger Electron Spectrometry (AES), Ultraviolet photoelectron spectroscopy (UPS), and X-ray Photoelectron Spectroscopy (XPS). Compact Toroidal Deflector Analyzers have also been proposed for use as add-on attachments to scanning electron microscopes, where they capture either the scattered secondary or backscattered energy spectra. However, improvements in designs of conventional energy spectrometers are desired.
In AES, the relatively high energy resolution capability of Hemispherical Deflector Analyzers (HDAs), which is around 0.05%, comes at a price of low transmission, typically at less than 0.15%. On the other hand, the better transmission performance of Cylindrical Mirror Analyzers (CMAs), being around 15% comes at a price of a poorer minimum energy resolution, which is typically between 0.2% and 0.3%. Hence, it can be appreciated that existing energy spectrometers are unable to provide both high transmittance (>15%) and high energy resolution (<0.05%). Further, existing energy spectrometers do not have the ability to perform parallel energy acquisition, in which output signals of different energies can be obtained simultaneously, greatly speeding up data-acquisition times. In this respect, while both the CMA and HDA operate sequentially, the HDA may be configured to operate in a partial parallel mode of operation for high energy resolution (>0.05%), where the output energy bandwidth is typically around 3% of the central-band energy.
As is known, the energy spectrometers in the Scanning Electron Microscope (SEM) have a variety of different applications, including quantitative voltage contrast from secondary electrons and material analysis/topography using backscattered electrons. Specifically, the possibility of carrying out Auger elemental analysis in the SEM was recently demonstrated just after cleaning a specimen's surface with an ion beam. This method is however only feasible for short data acquisition times, which in turn requires further improvements in the resolution-transmittance performance of present energy spectrometers. Moreover, it also requires widening the bandwidth in a parallel mode of operation. It will be also appreciated that energy spectrometers are needed for the Scanning Helium Ion Microscope (SHIM) for acquiring material analysis information from backscattered Helium ions.
One object of the present invention is therefore to address at least one of the problems of the prior art and/or to provide a choice that is useful in the art.